1. Technical Field
This invention relates to an oxide thin film having a widegap or transparency and p-type conductivity.
2. Background Art
Transparent conductive oxides such as ITO are controllable from an insulation of about 10.sup.-9 S/cm to a conductivity of about 10.sup.4 S/cm. Despite this outstanding characteristic, transparent conductive oxides are merely applied as transparent electrodes in flat panel displays and solar batteries. In the semiconductor application, a p-n junction is an important structure. However, since prior art transparent conductive oxides are all of n type and no transparent conductive oxides of p type are available, it is difficult to form a p-n junction solely from transparent conductive oxides. If formation of p-type conductive thin film becomes possible, it can be combined with prior art n-type semiconductor to form a p-n junction, which enables the fabrication of UV light-emitting diodes and transparent transistors.
For such a purpose, the inventor Kawazoe et al. reported that delafosite oxide exhibits widegap p-type conductivity (see Nature, No. 389, 1997, page 941, H. Kawazoe, M. Yasukawa, H. Hyodo, M. Kurita, H. Yanagi, H. Hosono "P-type electrical conduction in transparent thin films of CuAlO.sub.2 "). However, the thin film formation temperature is as high as 700.degree. C. There is a desire to have a thin film which can be formed at lower temperatures for wider application.